numbering add-in error message

[nora brinkley]

we have been using a purchase order form that has macros
in excel for about a year with no problems, but this week
we started getting the following error message "The
numbering add-in must be loaded for optimal numbering and
toolbar behaviour. Please load this add-in into your
library directory."

now the file does not calculate the oder values etc.

i have looked in the add-in section of the tools menu but
there is no add-in called numbering!

any suggestions?
have you come across this and how can i fix it?

thanks